Telephone-exchange system



Dec. 29, 1925- 1,567,249

L. DEVAUX TELEPHONE EXCHANGE S YSFEM Filed Oct. 9 1925' 2 Sheets-Sheet 1 m e: 0 mm mm-521m n.- 21.1" m: n math-aqua M u m LAW Mama (5 Dec. 29, 1925- 1,567,249

L. DEVAUX TELEPHONE EXCHANGE SYSTEM Filed Oct. 9, 192:5 2 Sheets-Sheet 2 Patented Dec. 29, 1925.

UNITED STATES LUCIEN DEVAUX, OF PARIS, FRANCE, ASSIGNOR TO WESTERN ELECTRIC COMPANY FATEWT OFFICE.

INCORPORATED, OF NEW YORK. N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

/ Application filed October. 9, 1923. Serial No. 667,470.

To all whom 2'25 may concern:

Be it known that I, LUCIEN Dnvnux, a

. citizen of the Republic of France, residing at Paris, in the Republic of France, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone ex change systems and more particularly to such systems as are adapted to provide service in a private branch exchange.

Systems of this character are usually arranged so that the apparatus of the private branch exchange may obtain connection with apparatus local to the exchange and is also enabled to obtain connection with a line leading to the main exchange to the exclusion of other apparatus.

It is the object of this invention to provide an improved system of this character. The invention will be more fully understood from the following description taken in connection with the accompanying drawings, Figs. 1 and 2 of which when taken together with Fig. 2 beneath Fig. 1, illustrating a system in accordance with the invention.

Each subscribers substation, two of which are disclosed in Fig. 1 of the drawings, is provided with the usual switchhook, receiver, transmitter, condenser, bell and induction coil connected in the well known manner. Further, each station is provided with a pair of keys 103 and 10 1 and an earth connection, the object of the keys being to connect earth to either of the conductors of the subscribers line. Each subscribers line leading to the exchange apparatus consists of two conductors only with a connection to ground at the substation and has associated with it three line relays. These line relays are indicated at 105,106 and 107. Each subscribers line extends through the back contacts of relay 105 to a key, such as, 221, located upon the operators keyboard through which key the subscribers line may be connected to other subscribers lines in the exchange or to a trunk circuit extending to the main exchange.

Only one trunk circuit 101, 102 has been disclosed extending tronrthe private branch exchange to the main exchange indicated in the left portion of Fig. 1, but it is obvious that additional trunk circuits with corresponding equipment may he added, as the traiiic between the branch exchange and the main exchange requires. The private branch exchange monitors head set is shown in the lower right corner of Fig. 2 and may be connected to a subscribers line of the private branch exchange through a key, such as, 220 or to the trunk line 101, 102 extending to the main exchange by key 260. It is thought that the invention may be more fully understood from the following description of the operation of the circuits disclosed.

It will be assumed lirst that the subscriber A desires to establish a local connection to the subscriber B at the same private branch exchange. The subscriber A removes his recciver which closes the substation loop across his line in the usual manner. The subscriber thereupon presses the key 104, which operation opens contact 110 and closes contact 111. The operation of depressing key 1 also permits the lower portion of the locking lug 112 to move into engagement with the lower moving spring of the key so that the contact 111 remains locked in its closed position for a short time after the key 10 1 is released by the subscriber. Contact 110, however, closes, as soon as the key 10% is released so that for an instant both contacts 110 and 111 are closed. \Vhen the key 104 has attained its uppermost position, the locking lug is forced away from the lower moving spring and contact 111 is again opened. The depression of the key 4 closes a circuit for relay 107 which may be traced from battery through the winding of this relay, the right armature and back contact of relay 106, the innermost left normal contact key 220, the inner left normal contact of key 221, the inner rightarmature and back contact of relay 105, upper contact of key 103 in its normal position, through the substation loop, contact 111 of key 10st to ground. Relay 107 energizes, closing a locking circuit which may be traced as previously described through the subscribers substation loop and thence over contact 110 as soon as key 10% reaches its normal position, the outer right armature and back contact of relay 105, the inner right normal contact of key 221, the inner right normal contact of key 220 and thence to ground at the left armature and front contact of relay 107.

Relay 107 at its. right armature contact closes a circuit for relay 222 which in turn establishes an obvious circuit for the call signal 254.

' The monitor at the private branch exchange upon noticing the operation of the call signal 25 1 depresses key 220 associated with the calling subscribers line A. This operation connects the subscribers line A through the innermost springs and alternate contacts of key 220, the left and right inner normal contacts of key 221 to conductors 223 and 224: which are connected to the monitors head set. In addition, the sub scribers line is connected over the left and right intermediate springs and alternate contacts of key 220 through the windings battery feed coil 225 to battery and ground, whereby the calling line and the monitors head set are supplied with talking current. The monitor then communicates with the subscriber A and ascertains the number de sired. it having been assumed that the sub scriber A. desires to communicate with subscriber B, the monitor depresses he 221 so as to connect the line of the calling subscriber to the conductors 226 and 227. This connection is established over the innermost springs and front contacts of key 221, the circuit previously traced fromthe subscribers line to the monitors head set being at the same time broken at the inner no "mal. contacts of key 221. The monitor having depressed key 221, releases key 220. Talking current is supplied to the calling subscribers line over the inner springs of key 221, through the left and right intermediate springs and normal contacts of key 229 and the windings of battery feed coil 228. Since relay 230 is included in series with conductors 22'? between the springs of key 221 and the battery feed coil 228, relay 230 becomes energized over the subscribers line A but performs no useful function at this time.

I The monitor now throws key 231 associated with the wanted subscribers line B and operates the magneto 232 to call the subscriber. Current from the magneto flows over conductor 228 the inner left. spring and alternate contact of key 231, the normal contacts of the inner left spring of key233, the inner right armature and back contact of relay 105, the upper contact of key 103 and thence through the call bell. of substation B. contact 110, the outer right armature and back contact of relay 105, the normal contacts of the inner right spring of key 233, the inner right spring and alternate contact of key 231, conductor 22 1, thence back to the magneto 232. The subscriber B upon hearing the call signal removes his receiver from the switchhook and the monitor upon hearing the response of the called subscriber depresses key so as to connect the subscribers line B directly with conductors 220 and 227. The monitor then releases key 231. The two subscribers A and B may now converse over the interconnecting link circuit 226, 227 both being supplied with talking current through the battery feed coil 228.. So long as either subscriber retains his receiver off its switchhook, relay 230 is main taineu energized. When, however, both subscribers have restored their receivers to their switchhooks, relay 230 deenergizes and closes a circuit from ground through its armature and back contact, the outer leftalternate contact of key 221 to battery through the relay 222 causing the operation of signal 25% and a second circuit in parallel therewith extending through the outer left alternate contact of key 233 to battery through the relay 23 1 which, in turn, causes the operation of signal 245. The monitor upon noticing the operation of these signals, releases the keys 221 and 233 thereby disconnecting the two subscribers lines from link conductors 226 and 227.

It will now be assumed that a subscriber, such as subscriber A, of the private branch exchange desires to establish a connection with the trunk circuit 101, 102 extending to the main exchange. For this purpose the exchange circuit is taken into use by the subscriber A to the exclusion of other subscribers of the private branch exchange.

It is to be remarked that battery 155. of the private branch is permanently charged when theezrchange line is idle from battery 156 at the main exchange over conductor 101, the circuit being as follows: Battery 156, resistance lamp 152, back contact of relay 148, conductor 101, outer right armature and back contact of relay 1 12, retardation. coil 15?, inner armature and back contact of relay 1 15 and through the battery 155 to ground. The potential of battery 155 being lower than the potential of battery 156, current flows continuously from battery 156 to the battery 155 so long as relays 142 and 145 are deenergized.

The subscriber A to initiate a call to the main exchange, depresses the key 103 of the substation thereupon closing a circuit for relay 106 which may be traced from battery through the winding of relay 140, right winding of relay 106, left armature and back contact of relay 107, inner right spring and normal contact of key 220, normal contacts of the inner right spring of key 221, outer right armature and back contact of relay 105, contact 110 of key 10-1, thence over the subscribens line loop, contact 1411 of key 103 to ground. Relay 106 thereupon energizes and closes at its left armature contact a lockcircuit which is independent of contact 111 of key 103, the contact 141 opening soon as the key 103 is entirely released. The locking circuit of relay 100 may be traced from ground through the left winding and left armature contact of relay 106, the right winding of relay 105, inner right armature and back contact of relay 142 to battery at the outer left armature and back contact of relay 148. Relay 105 energizes in the looking circuit of relay 106, connecting the conductors of the subscribers line over its right arinatures and front contacts through the windings of relay 144 to the conductors 101 and 102 of the trunk circuit extending to the main exchange.

When the subscriber at substation A has been connected to the conductors 101 and 102 of the trunk circuit, current flows from battery 156 at the main exchange over trunk conductor 101, the left high resistance winding of relay 144, the inner right armature and front contact of relay 105 thence over the subscribers line loop, returning over the outer right armature and front contact of relay 105, the right low resistance winding of relay 144, conductor 102 to ground to the winding of relay 147. Relay 147, upon energizing, in this circuit closes an obvious circuit for the signal 149 which thereupon glows, indicating to the main exchange operator that a call is incoming over the trunk circuit from the private branch exchange. The operator then responds by inserting pl 1; 151 into the jack 150', whereupon the cut otl relay 148 is operated in the usual manner disconnecting relay147 from the conductor 102 of the trunk line.

Relay 144 which also energized over the "flice trunk circuit, closes a circuit eX- g from battery through its armature front contact, the windings of relays and 143, the left winding of relay 105 ant left armature contact of this relay to 'i lllltl. Belay 145, upon energizing, opens he connection between the main exchange ery 156 and the private branch exchange cry 155 at its inner armature and back ct and at the front contact of this ar- 7 sure establishes a locking circuit for itself and for relays 143 and 105 independent of relay 144. Relay 143, upon energizing, opens the initial energizing circuit of relay 105 the outer left armature and back con ,ct of relay 143 and also opens the looking circuit previously traced'through the left winding of relay 106. Relay 106 thereupon deenergizes, At its inner left armature and front contact, relay 143 prepares a circuit for relay 158 which, however, is not operated until relay 144 becomes deenerd. At its right armature and front 'con- 1 ct, relay 143 establishes an obvious circuit for 154- which, in turn, operates the (i5 T 133 indicating to the branch exchange that the interoflice trunk circuit is it the outer armature contactof rea shunt is placed around the left sistance winding of relay 144 for of :tccting a more etlicient talking circuit be tween the subscribers line and the main exchange. Relay 144 is, however, maintained energized so long as either the calling subscriber maintains his receiver off his switchhook or the exchange operator retains the plug 151 in the jack 150.

If the apparatus at the main exchange is of the automatic type it may be readily ar ranged that this apparatus may be operated under the control of a calling device installed at the substation of the subscriber in the branch exchange. It will be observed that the circuit of relays 145, 143 and 105 is closed independently oi the contact of relay 144 so that if relay 144 vibrates in response to a calling dial on a branch exchange line when the subscriber dials the wanted line iuunher, the opening of this contact does not cause the deenergization of relays 145, 143 and 105 and the consequent disconnection of the calling line from the interoflice trunk.

it the end of the conversation when the subscriber hangs up his receiver, current ceases to flow over the interollicc trunk line and relay 144 deenergizes, completing at its armature and ha -l; contact, the circuit of relay 158 which relay in turn short-circuits relay 1457 This latter relay thereupon deener izes and at its inner armature and front contact opens the previously traced locking circuit extending through the windings of relays 143 and 105. Relay 143, upon deenergizing, releases relay 154, discontinuing the busy signal 133 and also opens the circuit of relay 158. All relays employed in the establishment of the connection are now in their normal positions. At the main exchange the operator receives the usual disconnect signal and takes the plug 151 from the jack 150.

Should the monitor desire to call the main exchange, the interotiice trunk circuit being resumed free, the monitor will depress key 260 t ierehy closing the circuit of relay 142 which ma be traced from battery through the right armature and back contact of relay 143, winding of relay 142, the outer right ing and normal contact of relay 229, the lettintermediate spring and alternate contact of key 200 to ground. Relay 142 energizes and at its left arniaturcs and front contacts connects thecoiuluctors 101 and 102 of the exchange trunk through alternate contacts and inner springs of key 260 to conductors 223 and 224 leading to the monitors headset. Should, however, the exchange line be busy relay 14-3 will be energized and the energized condition of this relay will prevent the closure of the circuit of relay 142 so that the moi'iitofs headset cannot be associated with the exchange line.

in order that the monitor may be apprised of the fact that the exchange line is busy, a circuit is established fer the vibrating relay 1 0 extending from battery through the III winding of relay 140, the inner left armature and back contact of relay 142, the inner left spring and alternate contact of key 260, conductor 223, thence through the monitors headset, conductor 224, the inner right spring and alternate contact of key 260 to ground at the left armature and back contact of relay 142 through-resistance 161. Relay 140 energizes in this circuit, short-'circuiting its own winding so that so long as the relay 142 remains deenergized, due to the busy condition of the interoflice trunk circuit, relay 140 intermittently operates thereby producing a tone in the receiver of the monitcrs headset.

Should another subscriber, such as the subscriber B, of the local exchange desire to call the exchange line when the latter is in use, as, for example, by the subscriber A, the subscriber B will depress the button 104 of the substation set thereby causing the energization of relay 106 over a circuit similar to the circuit described for the energization of relay 106 associated with the subscribers line A. The relay 106 closes at its inner right armature a circuit extending from ground through the right winding and inner right armature of relay 1.06, the right winding of relay 105, the inner right armature contact of relay 142 to the outer left armature of relay 143, but since the interoflice trunk has been assumed to be busy, relay 143 is at the time energized and the circuit of relay 105 cannot be completed. Consequently, the subscribers line B cannot be connected to the interofiice trunk circuit. Should the interofiice trunk line have been taken in use by the operator, the relay 142 will be at the time energized as previously described and the circuit of relay 105 cannot therefore be completed since it is open at the inner right armature and contact of relay 142. In order that the subscriber B may be informed of the busy condition'of the interoiiice trunk circuit, a circuit is established at this time from battery, through the winding of vibrating relay 140, the left winding of relay 106, left armature and back contact of relay 107,

inner right spring and normal contact of and normal contact of key 231, the outer armature and front contact of relay 106 to ground at the normal contact of key 246. Relay 140, due to the fact that its armature short-circuits its Winding upon each attraction therecf, vibrates producing a tone in the receiver of substation B.

hen a call is incoming from the central office, ringing current applied to the trunk conductors 101 and 102 passes through the left winding of ring up relay 262 which, upon energizing, locks in a circuit extending from battery through the intermediate left spring and normal contact of key 260 to ground at the intermediate armature of relay 262. At its outer armature and front contact, relay 262 establishes an obvious circuit for signal 263 for signaling the branch exchange monitor that a call is incoming. Relay 262 at its intermediate armature contact also establishes a circuit extending over the outer right spring and normal contact of key 229 through the winding of relay 142 to battery at the right armature and back contact of relay 143 for operating relay 142. Relay 142 immediately connects the conductors 101 and 102 of the interoflice trunk over its left armatures and front contacts to contacts of key 260. Relay 142 also disconnects battery at its inner right armature and back contact for preventing the operation of a subscribers line relay, such as 105, and the connection of a local subscribers substation to the interoifice trunk. Relay 262 also establishes a circuit over its inner right armature contact to battery through the call bell 244 to more particularly attract the private branch exchange monitors attention to the fact that a call is incoming from the main ofiice. In response to the operation of signal 263 and the ringing of bell 244, the monitor depresses key 260 completing the connection from the interoflice trunk 101, 102 with conductors 223, 224 extending to her headset.

Assuming that subscriber A is wanted, the private branch exchange monitor rings up the subscriber by depressing the key 220 and operating the generator 232 in the manner previously described in connection with calling the subscriber B. The interoflice trunk line isheld following the depression of key 220 by the retardation coil 259 which is connected across conductors 223 and 224 between the contacts of key 220 and key 260. hen the subscriber A has answered, the monitor transfers the connection by depressing key 246. The depression of key 246 closes a circuit over the alternate contact of this key, the outer left spring and alternate contact of key 260, the winding of relay 163 to battery at the right armature and back contact of relay 143. At the same time, key 246 breaks the locking circuit extending through windings of relays 106, 106, etc, of the different subscribers lines thus deenergizing any such relay which might at the time be in its operated position. Relay 163, upon energizing, closes a circuit which reestablishes the circuit of relay 105 broken at the back contact of relay 1-1-2 and which may be traced from battery, winding of relay 140, right winding of relay 106, left armature and back contact of relay 10?, outer right spring and alternate contact of key 220 to ground at the right armature and contact of relay 163. Relay 106 energizes thereby operating relay 105 as already described. The energization of relay 105 in turn causes the successive energization of relays 144, 1&5 and 1 18 as previously described. As soon as relay 1 13 energizes, the circuit of relay 142 is opened at the right armature and back contact of relay 143 and relay 14:2 becomes deenergized. The connection between the trunk circuit and the monitors set through the contacts of key 160, and between the subscribers set A and the monitors set through the con tacts of key 220, are broken respectively through the deenergization of relay 142 and the energization of relay 105, and the subscribers line and the main exchange become connected together as when the subscrlber A called the main exchange himself. Following the connection of the subscribers line to the main exchange, the private branch monitor may release keys 220 and 260. As soon as the conversation has terminated the connection is broken down and all apparatus restored in the manner previously described.

It will be obvious that any number otprlvate branch exchange lines may be provided as desired, it only being necessary to d upl1- cate the relays 105, 106 and 107 individual to each subscribers line. Further, a number of interottice trunk lines may be provided as desired, it only being necessary to duplicate relays 105, 105, etc., and to provide suitable circuits for the energizatlon of arelay associated with each additional trunk line in order to connect the calling lmes thereto.

Vshat is claimed is: I

1. In a telephone system, subscr bers lines, a trunk circuit, a monitors positlon, a pair of keys and a switchhook at the sub station of each line, means responsive to the operation of one 01 said keys and the operation of said switchhook to connect the re spective line to said trunk circuit, means responsive to the operat1on of the other of said keys and the operation of sa d swltchhook to signal said monitors position, and means controlled by said monitor to extend said line to said monitors position.

2. In a telephone system, subscribers lines, a link circuit, a trunk circuit, a momtors position, a pair of keys and a switchhook at the substation of each line, means responsive to the operation of one of said keys and the operation of said switchhook to connect the respective line to said trunk circuit, means responsive to the operation of the other of said keys and the operation of said switchhook to signal said monitors position, and means controlled by said monitor to extend said line to said link circuit and thence to a wanted line.

3. In a telephone system, subscribers lines, a trunk circuit, a monitors position, a pair of keys at the substation of each line, means responsive to the operation of one of said keys to connect the respective line to said trunk circuit, means responsive to the operation of the other of said keys to signal said monitors position, and means associated with said trunk circuit to prevent the concurrent connection of more than one of said lines thereto.

4:. In a telephone system, subscribers lines, a trunk circuit, a monitors position, a pair of keys at the substation of each line,

means responsive to the operation of one of said keys to connect the respective line to said trunk circuit, means responsive to the operation of the other of said keys to signal said monitors position, means under the control of said monitor to connect her position with said trunk line, and means associated with said trunk line for preventing the connection of a second subscribers line thereto concurrently with the connection thereof to another subscribers line or to said monitors position.

5. In a telephone system, subscribers lines, a trunk circuit, a monitors position, a

pair of keys at the substation of each line, means responsive to the operation of one of said keys to connect the respective line to said trunk circuit, means responsive to the operation of the other of said keys to signal said monitors position, means under the control of said monitor to connect her position with said trunk line, and means for transmitting a busy signal to a subscribers line or to said monitors position upon an attempted connection to said trunk line when it is engaged.

6. In a telephone system, subscribers lines terminating in a branch oilice, a trunk circuit incoming to said branch ofiice from a main otlice, a monitors position at the branch otfice, means responsive to a call incoming from the main oflice to signal said monitor and to extend a connection from said trunk circuit toward her position, and means elfective immediately thereupon for rendering said trunk circuit busy whereby said subscribers lines may not become connected to said trunk circuit through the initiation of calls on said lines.

7. In a telephone system, subscribers lines terminating in a branch otlice, a trunk circuit incoming to said branch office from a main office, a monitors position means responsive to a call incoming from the main office to signal said monitor, means con trolled by said monitor to extend a connection from her position to said trunk line, means individual to each line and controlled by said monitor for calling a wanted one of said lines, and a common transfer key for transferring the call incoming on said trunk circuit to said wanted line.

8. In a telephone system, subscribers two-conductor lines, a trunk circuit, a link circuit, a monitors position, a pair of keys at the substation of each line for grounding either sides thereof, means responsive to the operation of one of said keys to connect the respective line to said trunk circuit, means responsive to the operation of the other of saidkeys to signal said monitors position, and means individual to each of said lines and under the control of said monitor for connecting said lines to either said monitors position or to said link circuit.

9. In a telephone system, subscribers lines, a link circuit, a monitors position, a signal for each of said lines at said monitors position, means responsive to the initiation of a call on one of said lines for operating the signal thereof, means individual i to each of said lines and under the control of said monitor for interconnecting said lines over said link circuit, and means in said link circuit operative in response to the termination of a conversation between two I LUUIEN DEVAUX. 

